Parallel hydraulic control system



June 14, 1960 J. BRANDSTADTER 2,940,428

PARALLEL HYDRAULIC CONTROL SYSTEM Filed Aug. 10, 1954 SERVO AMPLIFIER INV EN TOR.

JACK BRANDS 7210727? WKf/W ATTORNEY matically.

United States Patent PARALLEL HYDRAULIC CONTROL SYSTEM JackBrandstadter, New York, N.Y., assignor to Bendix Aviation Corporation,Teterboro, N-L, a corporation of Delaware Filed Aug. 10, 1954, Ser. No.448,878

7 Claims. (Cl. 121-41) This invention relates generally to controlsystems and more particularly to control systems whose power means arefluid operated and are actuated manually and auto- In control systemshaving fluid operated power means, the characteristics of the controlleror transfer valve for the power means is such that, when the controlleris designed for optimum manual operation, the design usually does notpermit optimum automatic operation.

Conversely, when the control is designed for optimum auto- ;maticoperation, the design usuallydoes not permit optimum manual operation.

An object of the present invention; therefore, is to provide a novelservosystem whose power means is; ar-

ranged for optimum manual and automatic control.

Another object is to provide a servosystem whose'power means is manuallyand automatically controlled and has an arrangement'for safelytransferring control from manual to automatic. I i

A further object is to provide a novel servosystem 'whose fluid operatedpower means is selectively operable manually and automatically and inwhich the manually operable controller follows the operation ofthe'system by the automatic control.

A still further object is to provide a novel fluid operated servosystemwhich is selectively manually and automatically controlled but whereinthe manual control can override the automatic control.

The present invention contemplates a novel servosystem having a fluidoperated power means controlled from a pair of parallel connected flowcontrol means or actuators, one actuator being operated from amanualcontrol system and the other actuator beingoperated from an'automaticcontrol system. The novel arrangement {contemplated makes it possiblefor the manual control system to override the automatic control system.A

' novel interlock arrangement prevents the automatic control system fromopposing the operation of the power means by the manual control systemwhen the manual control system is to override the automatic controlsystem. A novel interlock release and low velocity device provides forreengaging the automatic control system for 'limited action of the powermeans until such time as consideration of the detailed description whichfollows, taken together with the accompanying drawing wherein oneembodiment of the invention is illustrated by way of'example. It is tobe expressly understood, however,

Y that the drawing is; for the purpose of illustration, and descriptiononly, and isnot intended as a definition of the limits of the invention.1 v V The single sheet of drawing illustrates schematically ItlliB novelservosystem of ithespresent invention incor- -pistons .43. and 45, pressthe pistons against shoulders Patented June 14, 1960 porated in acontrol system for operating the control surface of an aircraft.

In the novel servosystem illustrated as controlling an aircraft, ahydraulic ram 5 displaces a control surface 6 of the craft in responseto fluid flow actuation from one of two parallel control systems: theautomatic control system comprising an automatic pilot system 7 and atransfer valve 8; and the manual control system comprising 'a manuallyoperable stick 9 and a holding and interlock valve 10. A differentiallinkage 11 permits stick 9 to follow the operation by the automaticcontrol system. Solenoid operated valve 12 provides for engagement ofthe system, and solenoid operated valve 13 and a valve 14'provides forslow and safe transfer of control.

Turning now to the drawing, the novel control system is illustrated asbeing in condition for operating the aircraft control surface fromthe'automatic control system. Switch lever 17 is in a closed position sothat solenoid 19 isenergized from battery 21; Plunger 23 holds spool 25of valve 12 in a raised position against the bias of spring 27 andallows fluid from conduit 29 at system pressure to flow by Way ofconduit 31 to chambers 33 and 34 of the holding and interlock valve 10and by way of conduit 35 to a chamber 37 at onelend of cut-01f valve 39.This pressure fluid may be supplied by any conventional type pumpingsystem, only the pressure line 29 and drain or sump line 40 being shown.

The pressure fluid in chambers 33 and 34, acting against 47 and 49 tocenter and relatively fix spool 50. The pistons are designed to have anarea such that the force locking spool 50 in centered position is greatenough to hold the spool against the dynamic forces resulting from theinertia of stick 9 and linkages 11 when the craft is accelerated but notso great that the human pilot cannot readily overpower the lockingaction by movement of stick 9.

The pressure in chamber '37 moves spool '52 from a position against stop53 to the position, as shown, against -stop 54. This position of spool52 allows pressure fluid from conduit 57 to flow through conduit 59 andchannel 59A to transfer valve 8 and from transfer valve 8 to thehydraulic ram 5 through either conduit 60 or 61 and conduit 62 or 63.Channel 59A forms an annulus encircling spool so that pressure'fluid canflow throug valve 8 even though the spool is centered.

Transfer valve 8 may be generally similar to the valve described in US.Patent No. 2,625,136. In the embodiment herein, the pressure fluid flowscontinuously through conduit 59 to conduits 65 and 67 to chambers 68 and69 and through orifices 71 and 72 to sump. When a cantilevered armature73 is centered, the flow through orifices 71 and 72 is equal and spool75 remains in a center position. When armature 73 is moved to the rightor to the left of center the flow through one of these orifices isrestricted and a greater flow is permitted through the other. Theresulting differential pressure in chambers 68 and 69 forces spool 75 tothe right or left. Depending upon the direction of this movement, thepressure fluid from conduit 59 is conducted through a conduit 60 or 61,and a corresponding conduit 62 or 63 to one side of a piston 77 inhydraulic 'ram 5. Thus, the direction of movement of piston 77 iscontrolled by the direction and amount of movement of armature 73 fromits centered position.

Armature 73 is moved in response to output from an amplifier 80 which isthe signal from automatic control system 7. To this end, a pair of coils82 and 83 surrounding armature 73 are diiferentially energized inadirectionand-in amount corresponding to the phase 7 surfaces of thecraft, it'is illustrated herein as the elevator surface for purposes ofconvenience. The auto.-

. math: 'control system 7 for this surface may be of any :coriventionaltype and. is illustrated herein simply as be;

' ing comprised ofja signal chainincluding a follow-up inductive device85 and a pitch inductive device 37,. In

a well-known manner," inductive device 87 is connected to the' Gimbleaxis of a vertical gyroscope 88 for relative displacement as a craft isdisplaeed'frorn a predetermined pitch attitude to developa correspondingsignal. 'Aftenamplification inamplifier80,'tl1is Signal QP- cratestransfer.-valve 8 to actuatehydraulic ram unti 'opposite to the signal:from inductive device 87.

*armature 73 is centered 6is stopped.

' control'surface .6 has been moved an amount such that the signalresultingfromithe displacement of the rotor of inductive device 85relative tolstator is equal and net input signal to amplifier 8!! atthis time iszero and I 'In order that the human pilot may'have'knowledge of the operation of the surface 6 by the automaticcontrol system, the novel arrangement'includesitdilferential linkage 11'and the holding feature comprised of spool -50" and, pistons 43 and 45,The shaft of piston 77 of rams is connected to manual controller 9bydifferential,

' pivotedon a pin 92. During automatic operation, pist'ons' 43 and 45hold spool '50 centered I so thatpin 94 is in effect a fixed pivotpoint. Accordingly, the move: "mentof piston 77' rotates link 90 aboutpin 9.4; andlink 91 constrains controller 9 to follow the actionlof thesurface 6.

' :Summarizing the operation of the system under the automatic. controlconfiguration, the circuit formed by releases the pressure in loads 31and. 3.5. Spring 109A being stronger than spring 100B and overcoming theresidual pressure in chamber 37 drives spool 52 to the right againstabutment 53, cutting ofl? the operation of transfer valve 8 byautomatic'pilot system '7 so that the automatic control system can notoppose the manual operation. 'Moving spool 50 to the left 'or right ofthe center position shown n rmits pressure fluid from i n duit 102 to befed selectively to conduits 103 and 104 nd to eith side of piston 771 iH By momentarily overpowering the pressure exerted on locking pistons 43and 45 by the pressure fluid in diambsrs 33 nd 34, pil t relieves the flp suro pp and rend the auto i trolled transfer'valve '8 ineffective onram 5. Pistons 43'and 45 remain in their displaced position since thefluid pressure from conduit 31'and 35 is bled by con- Th a so thatdisplacement of surface closing switch 17 energizes solenoid 19, liftingspool' 25 'andpermitting pressure fluid to lock the manual'con'troltransfer valve 50 in center position and to open cut-out valve39 bymoving spool 52 against abutment 54. "The pressure fluid is supplied byway of conduits" 57, 59, 65 and 67 to chambers '68 and 69 or transferwaive 8 whose spool 75 remainscentered h'oth chambers. f

when the 'pressure is equal on iIShould the craft deviate,,however,fr'om' its predetermined attitude; the signal, which -isdeveloped atinduc:

.tive device 87 and which corresponds in phase andampli tnde' to theextent of direction of displacement, energizes coils 82;and 83differentially so asto move armature 73 Du ing th course-of manual fromm nual to autematioc ntr l nd the ut mati c nt ol he m lf n ti ing, th cntrol sur ce may be mo ed so rapidly as to p a e the cr ft adangeroattit e before the uman pilot can regain ntrol 'of the craf T opr snt inen ion obvi es t i possibility by l miti s o authority of the automs iontrol ystem upon initial engagement for a long enough interval'of timefor he human pilot to de erm ne wh h rth aut ru tic contro operatingsatisfactorily- 7 o roongagc he aut ma ic cont l system, s it h am 119 imo ed to a closed circuit po ition- This energiz s ,solsnoi i 11.2 frombattery 116; and pl er 71,18 moves spoo 1209f val e, 1. again t the b ofp i 3- Line pressure from conduit 29 is applied through conduit 124 tothe end ofspool 126, moving the spool to the lof ;T e p si i n f thelands f sp l 6 p mits pressure'fluid to flow from conduit 29 toconduit57; h we r, the action of orifice 2 8 estrict ths flo a and sons '5' isslowed As long as s l noid 1.12 is snorsiz d spool mounta s ingaposition displa sdto-th left. A conventional time-delayswitch 140isincluded inths circuit o solenoid 1 2- so that, a te a prede nor od oftime the so enoid tie-ene gized Th onduit 124 is releascd o ump l ne 4.0on

' to he biasing action oi sp s 13 returnin po l 120 tothe position sho nandsprin 1. 35 rs' srn spoo 12 6 19 th; normal pos ion hown ull ine prssure t eresftssi 'supph d t .tr nsforya1y ;8-an rani 5. The "a tomaticontrol 'systeniis aga n opera ng at ful opening and closingof'o'rifices' 71 and 72, a differential pressure builds up in chambers68 and "69-and moves spool 75 froni its center position, This setstip-a, differ V 'entia l pressure on piston 77 of hydraulic 'ram' 5driving the piston in a direction to operate'surfaee 6 tocor'recf' forthe deviationjof the 'craft from" its predetermined attitude, Piston 77moves-surface 6 until such timas V the rotor of inductive 'devicer85 isdisplaced to build up a signal equal and opposite t'o thesignal atinduetive j device;- 87. At this time, "the netinput to amplifier--80 iszero'and i-arrnature's B returnsto central position.

V'During' the course-of operationof the craft the automaticcontrolfjsy's'tem, the human pilot may desire to control thesurfacemanually; Moving controller 9 at this time pivots about pin anddisplaces {spool 50 from its center position. Displacement of -spool 511to the leftreleases the pressurein chambcr'33 through conduit 96inpiston 45 and conduit 97 to sump line40,

and displacement to the right releases; the press'ure'm chamber Mihfoughoonduits-osjsne -This also sis in a

. ment of the partswithout departm g fromthe spirit and scope of theinvention as will' now bennderstood-hythose 'skilledintheatt. p

news: yet snsyst l be overpo ered by h -manual controlle ias do rihs'dsho e a V The iorsgoins ha presen ed sino el .fiu d perated control sysem whereintw transfer w lv s arosonnsoto in pa allslifo tho: ope tion: oa hyd o' a o 1 al e b i oper ted r msnual y and the other tomati o llyrThs ma u l oper tion m y; ov ridol sht met c p rati n such whenashansisma or roinm noa r to automatic op ration; the oont o by th utomatic sytem is slowed for a inte l-of time so that a a etormination n he rniadotoo' whethor the automati c ntrol fsn tion nsprop rly b foros' omnlot ;relea e L o,: aut matis sont ol'is made: 7

Alth ugh only one sm odinien of. h in en i n ha been il ustrated anddescribed in detsi rit is to be exrr s y nd r o t nv t on. is notthereto- Various changeslean bemade in'the design .andiarranga andsecond flow control means, manual control means for operating said firstflow control means for controlling said power means, automatic controlmeans for operating said second flow control means for controlling saidpower means, and means for changing the control of said power means fromsaid first to said second flow control means including flow restrictingmeans for temporarily restricting the control of said power means bysaid second flow control means for a predetermined time after a transferof control from said first to said second flow 1 control means wherebyshould the automatic control means be malfunctioning, the power meansmay be controlled again manually before a dangerous control conditionarises.

2. In a servosystem, fluid operated power means, a source of pressurefluid, first flow control means operatively connected with said sourceand said power means for controllin the supply of pressure fluid to saidpower means and adapted to be operated by one control system, secondflow control means operatively connected with said source and said powermeans for controlling the supply of pressure fluid to said power meansand adapted to be operated by another control system, and aninterlocking system including pressure responsive cut off means biasedto a normal position for cutting off the supply of pressure fluid tosaid first flow control means, pressure operated locking means capableof temporarily locking said second flow control means in an inoperativeposition, control means operable in one sense for supplying pressurefluid to said out ofi means to urge the latter to a position to rendersaid first flow control means eflective and said control means includingmeans effective upon operation of said control means in said one sensefor supplying pressure fluid to said locking means to provide apredetermined force to lock and render said second flow control meansineffective, and other control means operative in a sense for providinga force for initially overcoming said predetermined force of saidlocking means to render said second flow control means efiective andsaid locking means including means effective upon operation of saidother control means in said sense for exhausting the pressure fluid atsaid locking means and at said cut ofi means so that said cut olf meansis biased to said normal position and said first flow control means isrendered ineffective.

3. In a control system, a fluid operated ram, a source of pressurefluid, first and second flow control means for regulating the supply ofpressure fluid to said ram, each having a movable spool for controllingsaid ram, a pressure operated valve between the pressure source and saidfirst flow control means resiliently biased to a position for cuttingofl the supply of fluid to said first of said flow control means, anautomatic control system for operating the spool of said first flowcontrol means, a manual control system for operating the spool of saidsecond flow control means, a centering arrangement for said second flowcontrol means comprised of a pair of pistons operatively connected tosaid source of fluid pressure for mov ing the spool to a centeredposition whereby the spool is rendered ineffective to control said ram,means for connecting said pressure fluid source and said valve wherebysaid valve is moved to a position permitting the flow of fluid pressureto said first flow control means to render the latter eflective, meansfor moving the spool of said second flow control means manually, andsaid pistons including normally closed fluid conduit means therein, theconduit means in one of said pistons bein adjustably positioned to anopen position upon manual movement of the spool of said second flowcontrol means, the conduit means of said one piston being so arrangedthat the opening thereof effects a releasing of the pressure fluidaction on said one piston and on said valve for causing said valve to beresiliently biased to the position for rendering said first flow controlmeans inefiective.

4. In a control system, for a surface of an aircraft,

fluid operated power means for moving said surface, a manually operabletransfer valve for controlling said power means, an automaticallyoperable transfer valve for controlling said power means, selectivemeans for operating said power means from one of said transfer valvesincluding means for normally holding said manually operable transfervalve in an inoperative position while said automatically operabletransfer valve is controlling said power means, means for rendering saidautomatically operable, transfer valveinoperativewhen said manuallyoperative transfer valve is manually moved from the inoperativeposition, and means for temporarily restricting the operation of saidautomatically operable transfer valve after a return to automaticcontrol is made from manual control.

5. In a servosystem of a type including a fluid operated power means, asource of pressure fluid, first and second flow control means forregulating the supply of pressure fluid to said power means havingconditions selectively effective for controlling said power means,automatic control means for operating said first flow control means,manual control means for operating said second flow control means,pressure responsive locking means providing a predetermined force forhydraulically locking said second flow control means in a conditionineffective to control said power means when said first flow controlmeans is in a condition effective to control said power means, and meansoperable for manually exerting a force on said locking means greaterthan said predetermined force so as to place said second flow controlmeans in a condition efiective to control said power means; theimprovement comprising said locking mea'ns including normally closedfluid conduit means, said fluid conduit means being opened upon saidsecond flow control means being placed by the manually operable means inthe condition efiective to control said power means, and valve meansoperatively controlled by the opening of the conduit means for placingsaid first flow control means in a condition inefiective for controllingsaid power means.

6. A system comprising fluid operated power means, a source of pressurefluid, first flow control means operable by one control system forcontrolling the supply of pressure fluid to said power means, secondflow control means operable by another control system for controllingthe supply of pressure fluid to said power-means, third flow controlmeans having first and second positions and being biased to said firstposition for cutting off the supply of pressure fluid to said first flowcontrol means, locking means capable of temporarily locking said secondflow control means in an inoperative position, means operable forsupplying pressure fluid to said third flow control means and saidlocking means, whereby said third flow control means is urged to saidsecond position to render said first flow control means eflective forcontrol of said power means and whereby said locking means provides apredetermined force to lock said second flow control means in aninoperative position, and means providing a force greater than saidpredetermined force for overcoming said predetermined force so as toadjustably position said locking means to render said second flowcontrol means etfective for control of said power means and said lockingmeans including conduit means therein efiective upon such positioning ofthe locking means to vent the pressure fluid from said third flowcontrol means so that the latter is returned to said first position andsaid first flow control means is rendered inefiective.

7. In a servosystem for a craft, a fluid operated power means for movinga surface of the craft, first and second flow control means selectivelyeffective for controlling said power means, automatic means foroperating said first flow control means, fluid operated means connectedto said second flow control means to normally prevent said second flowcontrol means from operating said power means, auxiliary control meansselectively positioned =ua1 means operativelyconnected -to' said secandflow'con References Cited inthe file of this, patent UNITED STATESPATENTS {:91 means, a'pd'yalve means'operated by manual operafion ofsaid manual meaqs to aias'e said auxiliary cont-r61 means to bejglec-tively pbsitiened so as to render said first flqw control means-inoperat-i-v e'm automatic operation, and said manual operation of saidmanual mgans being affective to dverprwer said fluid operaied' means andprovide'for central of said power means-manually 'bysaid second flowcontrol means.

- Akerri a'nn Apt; 191,192 1 fiall nheck -7 Sept. 29, 1936

